1. Non-equilibrium properties of an active nanoparticle in a harmonic potential
- Author
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Hana Šípová-Jungová, Alois Würger, Falko Schmidt, Giovanni Volpe, Mikael Käll, University of Gothenburg (GU), Chalmers University of Technology [Gothenburg, Sweden], Laboratoire Ondes et Matière d'Aquitaine (LOMA), and Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,Thermodynamic equilibrium ,Science ,FOS: Physical sciences ,General Physics and Astronomy ,Nanoparticle ,Physics::Optics ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Nanoscience and technology ,Critical point (thermodynamics) ,Position (vector) ,0103 physical sciences ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,010306 general physics ,ComputingMilieux_MISCELLANEOUS ,[PHYS]Physics [physics] ,Nanophotonics and plasmonics ,Multidisciplinary ,Condensed matter physics ,Rotational diffusion ,Nonlinear phenomena ,General Chemistry ,021001 nanoscience & nanotechnology ,Boltzmann distribution ,Soft Condensed Matter (cond-mat.soft) ,Particle ,0210 nano-technology ,Beam (structure) - Abstract
Active particles break out of thermodynamic equilibrium thanks to their directed motion, which leads to complex and interesting behaviors in the presence of confining potentials. When dealing with active nanoparticles, however, the overwhelming presence of rotational diffusion hinders directed motion, leading to an increase of their effective temperature, but otherwise masking the effects of self-propulsion. Here, we demonstrate an experimental system where an active nanoparticle immersed in a critical solution and held in an optical harmonic potential features far-from-equilibrium behavior beyond an increase of its effective temperature. When increasing the laser power, we observe a cross-over from a Boltzmann distribution to a non-equilibrium state, where the particle performs fast orbital rotations about the beam axis. These findings are rationalized by solving the Fokker-Planck equation for the particle’s position and orientation in terms of a moment expansion. The proposed self-propulsion mechanism results from the particle’s non-sphericity and the lower critical point of the solution., For active particles with nanoscale dimensions the overwhelming rotational diffusivity usually masks their residual non-equilibrium character. Here Schmidt et al. show how to amplify it in a suitable experiment to let a nanosphere rotate spontaneously around the beam axis in an optical trap.
- Published
- 2021
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